Leakage in the cavity of an acoustic sensor is traditionally detected by measuring the sensor's response to acoustic signals at very low frequencies (for example, frequencies below 100 Hz). This can be a challenging and costly measurement step oftentimes entailing limitations related to the types of leaks that can be detected. Clearly, such cavity leaks are undesirable and need be detected if for no other reason than for quality control purposes.
An acoustic sensor is currently tested for cavity leakage during manufacturing through application of an external acoustic stimulus, as is well-known to those skilled in the art. It is also known to those skilled in the art that this testing method may have limitations in detecting certain undesirable leakage paths, therefore creating a risk in manufacturing defective acoustic sensors.
By way of example, traditional acoustic leakage tests involve applying an acoustic signal to the sensor element using a test speaker that is connected to the sensor input through an acoustic channel. A tight seal is formed between the acoustic sensor input and the acoustic channel typically using a gasket. These traditional acoustic leakage tests can reliably quantify the leakage path between the cavity and the acoustic sensor input by measuring the acoustic sensor's response to low frequency acoustic inputs as described earlier.
However, traditional tests have difficulty measuring the leakage path from the cavity to the outside world. Accordingly, both leaks cannot be measured using conventional testing methods. Furthermore, the capability of testing the acoustic sensor in the field, requiring a test speaker, can be costly.
Therefore, the need arises for an acoustic sensor system that allows testing of its acoustic sensor in the field, with reduced costs, and measurement of multiple cavity leaks.